Deployment with Zend Server (Part 6 of 8)

This is the sixth in a series of eight posts detailing tips on deploying to Zend Server. The previous post in the series detailed setting job script status codes.

Today, I'm sharing some tips around setting up page caching, and jobs for clearing the Zend Server page cache.

Tip 6: Page caching

Zend Server offers page caching. This can be defined per-application or globally. I typically use global rules, as I most often define server aliases; application-specific rules are based on the primary server name only, which makes it impossible to cache per-hostname.

I define my rules first by setting up my rules using regular expressions. For instance, for my current site, I have this for the host:

(www\.)?mwop.net

This allows me to match with or without the www. prefix.

After that, I define regular expressions for the paths, and ensure that matches take into account the REQUEST_URI (failure to do this will cache the same page for any page matching the regex!).

When I deploy, or when I run specific jobs, I typically want to clear my cache. To do that, I have a Job Queue job, and in that script, I use the page_cache_remove_cached_contents() function defined by the page cache extension in Zend Server.

This function accepts one argument. The documentation says it's a URL, but in actuality you need to provide the pattern from the rule you want to match; it will then clear caches for any pages that match that rule. That means you have to provide the full match — which will include the scheme, host, port, and path. Note the port — that absolutely must be present for the match to work, even if it's the default port for the given scheme.

What that means is that in my example above, the argument to page_cache_remove_cached_contents() becomes http://(www\\.)?mwop\\.net:80/resume. If I allow both HTTP and HTTPS access, then I also will need to explicitly clear https://(www\\.)?mwop\\.net:443/resume. Note that the regexp escape characters are present, as are any conditional patterns.

My current cache clearing script looks like this:

chdir(__DIR__ . '/../../');

if (! ZendJobQueue::getCurrentJobId()) {
    header('HTTP/1.1 403 Forbidden');
    exit(1);
}

$paths = [
    '/',
    '/resume',
];

foreach ($paths as $path) {
    page_cache_remove_cached_contents(
        'http://(www\.)?mwop\.net:80' . $path
    );
}

ZendJobQueue::setCurrentJobStatus(ZendJobQueue::OK);
exit(0);

If I wanted to get more granular, I could alter the script to accept rules and URLs to clear via arguments provided by Job Queue; see the Job Queue documentation for information on passing arguments.

I queue this script in my post_activate.php deployment script, but without a schedule:

$queue->createHttpJob($server . '/jobs/clear-cache.php', [], [
    'name' => 'clear-cache',
    'persistent' => false,
]);

This will schedule it to run immediately once activation is complete. I will also queue it from other jobs if what they do should result in flushing the page cache; I use the exact same code when I do so.

Note on cache clearing

The Zend Server PHP API offers another function that would appear to be more relevant and specific: page_cache_remove_cached_contents_by_uri(). This particular function accepts a rule name, and the URI you wish to clear, and, as documented, seems like a nice way to clear the cache for a specific URI as a subset of a rule, without clearing caches for all pages matching the rule. However, as of version 7.0, this functionality does not work properly (in fact, I was unable to find any combination of rule and url that resulted in a cache clear). I recommend using page_cache_remove_cached_contents() only for now, or using full page caching within your framework.

Next time…

The next tip in the series discusses using the Zend Server SDK for deploying your application from the command line.